Segmented Source Drain Select Lines for 3D NAND Memory Erase Control
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Solution Overview
Problem
Three-dimensional NAND memory structures increase memory density but result in larger erasable block sizes, leading to inconvenient or intolerable increases in the number of simultaneously erasable pages, which is not desirable in many applications.
Innovation Solution
The solution involves segmenting global source and drain select lines within each physical block to create smaller erasable sub-blocks, with segmented drain select lines corresponding to segmented source lines, and designing junctions with different breakdown voltages to prevent erase disturb in adjacent non-selected sub-blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If three-dimensional NAND memory structures are used to increase memory density, then storage capacity is improved, but erasable block size increases leading to inconvenient or intolerable increases in the number of simultaneously erasable pages
Solution Approach 1:
The memory block is divided into multiple sub-blocks, each with its own segmented source and drain select lines. This segmentation allows the memory to be erased in smaller, more manageable units rather than requiring erasure of the entire large block, thus resolving the contradiction between maintaining high density and reducing erasable block size for ease of operation
Solution Approach 2:
The patent implements dynamic control of segmented source and drain select lines, allowing flexible selection and erasure of specific sub-blocks as needed. This dynamic capability enables the system to adapt erasure operations to actual needs, maintaining high density while providing operational flexibility comparable to smaller block sizes
2Ease of operation
If segmented source and drain select lines are used to create smaller erasable sub-blocks, then erasable block size is reduced, but device complexity increases
Solution Approach 1:
The patent extends the select line structure into the vertical dimension with multiple tiers of segmented source and drain select lines. This three-dimensional arrangement allows for complex sub-block segmentation without proportionally increasing planar complexity, as the segmentation is organized across multiple levels rather than requiring extensive lateral routing
3Reliability
If junctions with different breakdown voltages are designed to prevent erase disturb, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements different breakdown voltage characteristics at different locations within the memory structure by designing first and second junctions with asymmetric dopant profiles. This local differentiation allows specific junctions to have tailored electrical properties that prevent erase disturb in non-selected sub-blocks, with the asymmetric doping providing inherent robustness against manufacturing variations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for smaller erasable block sizes while maintaining high memory density, preventing unintended erasure of memory cells in non-selected sub-blocks during an erase operation, thus addressing the issue of increased block size in 3D memory arrays.
Implementation Method 1
Each of the drain select devices has an asymmetric dopant profile. The asymmetric dopant profile is configured to prevent an erase disturb of non-selected ones of the sub-blocks during an erase operation.
Data Source
AI summary
Various embodiments comprise apparatuses such as those having a block of memory divided into sub-blocks that share a common data line. Each of the sub-blocks of the block of memory corresponds to a respective one of a number of segmented sources. Each of the segmented sources is electrically isolated from the other segmented sources of the block of memory. Additional apparatuses and methods of operation are described.